If You are playing as Bachelor or Haruspicus and if You want to get bad ending, You need to complete the first day's main quest and survive until the end of the 12-th day. If You are playing as Devotress and if You want to get bad ending, You just need to survive until the end of the 12-th day. If You want to get character's own ending, You also need to have all Your adherents alive and well. When You cannot complete the day's main quest, one or two of Your adherents can get ill. You need to have "powder" or "panacea" to cure them. You can't enter into house if adherent got sick. There is no adherent's deaths in Bachelor scenario if You cannot complete day's main quest (Vlad Jr. can die in 8-th day if you will make a mistake, but if You missed 8-th day's main quest, he will be alive and his father dies). Of course, Eve will die in 7-th day, but she will die ANYWAY, You can't save her. Her death can't prevent you from getting good ending.
How to survive in this game:
You have few parameters: health, hunger, tiredness, infection, immunity, reputation. When Your hunger, tiredness or infection rises up to 100%, Your health will decline. The main problem is hunger: it's really impossible to collect so much food as you need on my first day's route, but it's possible to collect 11 empty bottles. My first day's roure passes near 3 food shops and a lot of dumpsters, so I could buy some food and find 10 bouttles. The last one bouttle Bachelor has in inventory from the beginning of the game. When you drink water, Your hunger will decrease by 1% and Your tiredness will increase by 3%, so when You drink 11 bottles 3 times, your hunger will decrease by 33% and Your tiredness will increase by 99%. But your tiredness will change three times faster than hunger when you are sleeping. You need to have 11 bottles, open house with bed and a water barrel roll near that house. I used Maria's house because she cannot get ill in Bachelor's scenario, but it's possible to use Eve's house because her house is open even when/if she is dead and there is a water barrel roll near her house. In my second speedrun with rule "Bachelor's ending" I used Ann's house, but it was harder because Ann is Devotress's adherent, so she might get sick (randomly). I think it's possible to survive without food, but it will be longer and harder. Also, You can get three free food items near Nina's crypt: random combinations of milk and bread. Bread is the best food in this game: it costs half the price of fresh meat/fish, but it decreases hunger at 24% (fresh meat/fish - 25%).
The main trick for both of my runs is diagonal movement: it's slightly faster to walk with "W"+"A" or "W"+"D" then simply forward. There is no run mode in this game.
It's impossible to enter Maria's house in 11-th day in Bachelor scenario, but it's possible to enter in 10-th day and sleep until 12-th day, so You need to collect some food. Of course, it's possible to go out in 11-th day.
When you wake up after midnight, screen stops for a second, but this second can be used blindly because You can control Your character.
When You are sleeping, You may move cursor to the right place, so You can save about a second when You wake up and open inventory.
It's possible to jump over the railing of Victor's and George's houses. It may save few second. I didn't use this trick in my speedrun with rule "bad ending" because I found this trick later and I couldn't beat my first time even with this trick.
As i know, the game can't end when You are in the Cathedral in the end of the 12-th day. Game will be over after midnight of the 12-th day after exiting the Cathedral and after time change (1 in-game minute = 5 real seconds). As You can see, I finished my second speedrun when in-game time was 0:06 (13-th day).
How to get Bachelor's ending:
Bachelor's adherent (utopians): George Kain, Victor Kain, Andrei Stamatin, Petr Stamatin, Vlad Jr. (can't get ill or die if 8-th day's quest is skipped), Maria Kain (can't get ill, but just in Bachelor's scenario), Eve Yahn (she dies according to the story), Mark Immortal (he can't get ill or die anyway). You need to collect 4 medicines (powder or panacea). The fastest way to get it: Lara's quest at first day (powder), Laska's dialog at third day (powder), Ann's and Lara's quest at 9-th day (two panaceas). If all character's adherents are alive and well, You need to visit the Cathedral and talk to general Block about town's fate. If You will not visit the Cathedral, or if You can't (because one or more of Your adherents is ill or dead), You will see bad ending.
I made few mistakes, but most of them due to engine bugs. There is a LOT of bugs in this game! The worst bug I met is "sticking". Character may stop suddenly when he goes near walls or some objects. Sometimes it's possible to unstick Your character just looking around, but sometimes you need to jump. You will lose about a second anyway. Another ugly bugs are "unfinished loading" (game starts when not all objects are loaded) and "slow town update". Both of them looks like freezing. Anyway, I think, all my mistakes are noncritical.
Unfortunately, I know nothing about differences between original (russian) "Мор. Утопия" and "Pathologic" versions (except language, of course). Maybe there are logical differences.
With best regards, Vlad.